CONTENTS
- INTRODUCTION
- STEP ONE: ARRANGE THE ROOM LAYOUT CORRECTLY
- STEP TWO: ADD BASS TRAPS IN THE CORNERS
- STEP THREE: CREATE A REFLECTION-FREE ZONE (RFZ)
Do I really have to learn all this? Can’t I just buy something simple that works?
Room acoustics presents the engineer/listener with a conundrum. Do you want to learn about acoustics and intelligently design an acoustic treatment strategy for your room, or just buy a simple package to immediately improve your sound?
If your answer is the former, then there are some DIY design ideas on this page to get you started. If you don’t like these designs, there are dozens of other designs online.
If your answer is the latter, then you can look at the custom package from RealTraps that I designed (link coming soon); it is my conception of a thorough, modular room treatment package that is customizable enough to fit in nearly any room one would encounter, built with normal, domestic or commercial construction techniques. It contains everything most people need to make average-sized home recording rooms, small commercial recording rooms, and listening rooms sound exceptional, with a lot of flexibility for different listening, recording, mixing, and mastering scenarios.
This page is a basic how-to in making a room used for music (playing, recording, or listening) sound good. It is ideal for home recording studios and listening rooms, and it has particular emphasis on a one-room studio design, with the goal of providing superlative sound in multiple contexts. Whether you are recording a full band, doing vocal overdubs, or doing careful listening (ie, for mixing, mastering, or audiophile listening) your room will excel.
This is a primer, not a doctoral dissertation
This how-to is not designed to be a thorough explanation of room acoustics, but rather a simple, solution-oriented primer that enables you to learn just enough to get good sound, not overwhelm you with information. If you get through this and want to learn more, there are many places on the web to research small room acoustics. None of the information on this page is new information; I’m going more for “useful distillation” of ideas out there, and specific, simple steps to make any room sound better. The best place to begin learning more than the basics presented on this page is Ethan Winer’s Acoustic Treatment and Design for Recording Studios and Listening Rooms. This article goes into great detail in presenting the next level of small room acoustics and the treatments necessary to achieve good sound. Beyond that, the reference standard is a book called The Master Handbook of Acoustics by F. Alton Everest. There is more than enough info in this book to satisfy the curiosity of anyone but the most hardcore acoustics geek.
‘Soundproofing foam’?!?!! Flee for the hills!
This how-to is not designed to be a tutorial in “soundproofing.” Soundproofing is the idea of keeping sound energy in the studio in the studio, and of keeping sound energy out of the studio out of the studio. Accomplishing this effectively, even in the low bass frequencies, is not a trivial task; it requires lots of mass, and specific construction techniques. That’s right, the “soundproofing foam” you just bought won’t actually “soundproof” anything. Soundproofing is an entirely different problem than making the room sound good inside, and I do not address soundproofing at all. If you are interested in learning about this aspect of room design, I highly recommend Rod Gervais’ book, Home Recording Studio: Build It Like The Pros. It discusses these concepts in great detail.
Small, domestic rooms
Most of us have small rooms for playing, listening, and/or recording in our home. In this context, “small room” means anything less than 20×30 feet with 8 foot ceilings (though this would still arguably be a small room). Most of the time these rooms are rectangular, and built using normal construction techniques for homes.
In this type of a room, and really in any room, there are three steps you can take to dramatically improve the sound. The first step involves no cash outlay, it is simply putting what you have in the best places to sound good. The other two steps will give examples of room solutions from RealTraps (an acoustics company I am affiliated with) products, as well as a variety of DIY solutions.
STEP ONE: ARRANGE THE ROOM LAYOUT CORRECTLY
If sound quality is important to you, then you will need to arrange the room in an acoustically beneficial way that will give you optimum stereo imaging, and minimize the effect of room modes on the bass.
Follow these steps:
- Have the listening position be centered between the 2 longest walls, facing one of the shorter walls. The 2 longest walls will be to your left and right. Your head should be 38% of the length back from the front wall, leaving 62% of the length behind you toward the rear wall.
- The speakers should be arranged so that they form an equilateral triangle with your head at the listening position. The tweeters should be at ear-level.
- Everything in the room should be symmetrical from left to right, particularly from the listening position forward.
This is step one, and it alone should make things sound better. Things will be more even and balanced, less bass distortions and much improved stereo imaging. It also puts you in position to have a really outstanding room with the right treatments.
STEP TWO: ADD BASS TRAPS IN THE CORNERS
Next you will want to put bass traps in as many corners as you can manage, to even out the low-end of the room. Many rooms have a drastically uneven low end response (caused by comb filtering), sometimes resulting in the “one-note bass” phenomenon and making nuances in the bass instruments difficult to discern. Dynamic peaks and valleys of up to 30dB or more, in extremely narrow frequency bands, are quite common in small rooms.
The solution is to add as much bass trapping in as many room corners that you can manage. There are several ways to do this, ranging from simple (buy the traps, hang them up) to complex (research, study, learn, design and build your own treatment options) and come in at a variety of budgets. Here are two effective options, one DIY, one not:
- RealTraps MondoTraps and Tri-Corners. Install MondoTraps straddling every corner, including the wall/ceiling corners, wherever they will not be blocked by a door or window. Also Tri-Corners in every part of the room where 3 walls come together (ie, wall/wall/ceiling, wall/wall/floor), wherever they will fit, preferably 8 of them for all the tricorners in the room.
- DIY Cotton Corner Absorber. The corner absorber is a familiar concept, with many different designs out there with varying degrees of effectiveness and cost. This design has a few goals in mind:
- Be Inexpensive
- Perform well
- Be easily removeable (many of us are in rental properties)
- Class-A fire rating
- Be as green and nontoxic as possible.
In order to accomplish all these goals, it uses a specific product for the absorption material, Ultratouch cotton insulation. You can build a similar product out of rockwool or rigid fiberglass, but cotton is inexpensive (especially if you have a dealer near you), and it is green (non-itchy, non-toxic, made from recycled denim).The cotton comes in roughly 2′x8′ batts, that are 5.5″ thick (it is available in different thicknesses). There are 16″ wide and 24″ wide models; the corner absorber uses one of each. The cotton is quite limp and floppy, it is also compressible. It is effective acoustically, but it isn’t as as neat as rockwool, much less rigid fiberglass. Covering the cotton with a cloth wrapping doesn’t give the sharp edges we are used to with acoustic treatments; therefore a custom “speaker grille” panel covering the cotton is beneficial.To build the absorber, simply put a 16″ batt straddling the corner, but a 24″ batt directly over the 16″ batt, and then cover the whole thing with a false, cloth-covered panel. A more specific design is coming soon, but in the meantime you can DIY it anyway you wish, as long as the cotton batts are held in place and you are happy with the cosmetic front panel, you’re golden.
- Better Yet: Both/And
Alternatively, one can combine these methods. DIY corner absorbers, with a MondoTrap (or 2 MiniTraps) installed over it gives fantastic performance. You get the raw absorption from the corner absorbers, and the MondoTrap gives you another whallop of bass trapping. At the same time, the membrane design will reflect high frequencies so as not to over-deaden the room.
Either way, the goal is to treat as many room corners — including wall/ceiling and even wall/floor corners — as possible. Doing so will even out the low-end response of the room, making low frequency instruments (kick drums, bass amps, subwoofers, etc) sound better, and make it easier for you to get the low end right while mixing.
STEP THREE: CREATE A REFLECTION-FREE ZONE (RFZ)
Ethan Winer explains RFZ:
The concept is very simple - to prevent “early reflections” from obscuring the stereo image. This occurs when sound from the loudspeakers arrives at your ears through two different paths - one direct and the other delayed after reflecting off a nearby wall.
In order to eliminate these reflections, we use absorbers at the first-reflection points. These panels don’t need to be as thick, but if they are thicker and spaced from the wall they will absorb to a lower frequency. So how do you find your first reflection points?
Mirror, Mirror, On The Wall….
The famous mirror trick. Have a friend come help you with a mirror he/she can hold up against the wall, at your ear level. You will be sitting at the mix position. Have your friend move the mirror around the walls. Anywhere you can see your monitors in the reflection of the mirror, install absorption. This will give you a RFZ, and you will be amazed at the increased level of detail you can hear in the stereo imaging. Width, depth, impact are all improved.
Side Wall Absorbers
Side Wall Absorbers are needed to absorb the first reflections from the left and the right. Here too, there are commercial and DIY choices. You can build absorbers covered with cloth out of 2″ of 703 rigid fiberglass, rockwool, or R13 Ultratouch cotton. A piece of R13 cotton, 24″ wide, cut in half makes a nice 4×4 absorber if you frame it out and cover it with cloth. From RealTraps I recommend the RFZ Panel or the MicroTrap for this application, though MiniTraps (HF version) do this job very well too.
Ceiling Cloud Absorber
In addition, you will want to make a ceiling cloud of some kind. If you are in a basement you can put Ultratouch between the ceiling joists and cover the bottom of the joists with cloth. Or you can build a similar 4×4 panel to the side wall absorbers (though you may want a 4×8 cloud, or a custom size for your room), hung from the ceiling. You can use the same RealTraps products for this as the side wall absorbers in the previous paragraph.
Better Yet Mark Two: Both/And
One of my favorite ceiling treatments for a listening room is a combination of RealTraps and DIY. Install a drop ceiling in the room. Put RealTraps Ceiling Tiles in it, and then stuff the space above the drop ceiling and below the joists with Ultratouch cotton. I’d use the normal RealTraps around the edges of the room for maximum bass trapping, and I’d use the HF RealTraps design both above the mix position and above any crucial recording areas, such as above a drum kit. This design will give superior performance: maximum bass trapping, without killing the room.
That’s it!
Congratulations. In the vast majority of cases, taking this 3 steps means that you’re 95% of the way to a good-sounding room. From here, some moveable panels that allow you to experiment with changing the way the room sounds are a very good idea. Gobos are great if you will be recording bands. Putting some diffusors in a room where these 3 steps have been taken, and things can really start to sound good.
(disclaimer: I am an employee of RealTraps, but this page is not a commercial page. It is an educational one. I’m not here to pimp gear. Some people want to DIY, saving money in the process. This is probably the most economical way to treat your room, depending on the value of your time and your technical skill. I include my take on DIY options every step of the way on this page. Others don’t have the time or inclination to DIY, and want quick, easy solutions. For this audience, I include RealTraps products in my recommendations on this page. The goal of this article is to educate about acoustics, providing real-world solutions.)
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